Regulator responsive to the electrical conductivity of a solution



Jan. 27, 1953 A. w. SMITH 2,626,620

REGULATOR RESPONSIVE TO THE ELECTRICAL CONDUCTIVITY OF A SOLUTION FiledAug. 30, 1948 4 Sheets-Sheet l z IN VEN TOR.

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AYTORNEYfi Jan. 27, 1953 A. w. SMITH 2,626,620

REGULATOR RESPONSIVE TO THE ELECTRICAL CONDUCTIVITY OF A SOLUTION FiledAug. 30, 1948 4 Sheets-Sheet 2 INVENTOR.

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Jan. 27, 1953 w. sMlTH 2,626.620

REGULATOR RESPONSIVE TO THE ELECTRICAL CONDUCTIVITY OF A SOLUTION FiledAug. 50, 1948 4 Sheets-Sheet 3 INVENTOR.

@PMQE Jall- 1953 A. w. SMITH 2,626.620

. REGULATOR RESPONSIVE TO THE ELECTRICAL CONDUQTIVITY OF A SOLUTIONFiled Aug. 50, 1948 4 Sheets-Sheet 4 7/8 fiE J I INVENTOR.

Mag-s.

Patented Jan. 27, 1953 REGULATOR RESPONSIVE TO THE ELEC- TRICALCONDUCTIVITY OF A SOLUTION Albert Woodall Smith, Kenmore, N. Y.Application August 30, 1948, Serial No. 46,864

18 Claims.

This invention relates to a regulator responsive to the electricalconductivity of a solution and is more particularly described inconjunction with a detergent feeder wherein the concentration of adetergent solution being used is maintained by additions of thedetergent under automatic control of a regulator responsive to theelectrical conductivity of the solution.

In the type of milk or cream can washing machine used in a dairy it iscommon practice to pump a wash solution from a sump tank and deliver itunder pressure through'spray jets to the inside and outside walls of apassing line of cans.

The wash solution usually contains a suitable detergent and is heldbetween a minimum of 140 F. and a maximum of 150 F. generally by athermostatic control set at some selected point within this range. Itwas found that detergents of a caustic nature such as sodium hydroxidewould damage the tin coating on the cans and use of this as a detergentwas discontinued in favor of milder alkalies such as sodium carbonate,trisodium phosphate, sodium metasilicate, sodium sesquisilicate or, acombination of these. Detergent powders ai'e' now commercially suppliedto dairies and which in addition to the above milder alkalies contain ahigher polyphosphate and a wetting agent or synthetic detergent forconditioning the water, preventing preciptation of water hardeningingredients, and enhancing the detergency of the wash solution. Withsuch alkalinedetergent solutions as used in washing milk cans and thelike, it is important that the strength of the detergent solu tion bemaintained within relatively close limits. For example, the New YorkCity Board of Health requires an alkaline detergent can wash solution tobe held between 0.05% and 0.10% active alkalinity as sodium hydroxide tophenolphthalein.

In recent years an acid detergent has been used as an alternative to analkali detergent. such acid detergents comprise an organic acid and awetting agent or synthetic detergent. Such acid detergents have beenfound to give best results at a pH of from 6.7 to 6.8, the latter being,of course, quite close to the neutral point.

The present practice in bottle soakers is to use a wash solution around2 of sodium hydroxide with trisodium phosphate to improve the rinsingproperties of the solution, as sodium hydroxide is diflicult to wash ofithe walls of the bottles, and it is usual also to apply a wetting agentand synthetic detergent. It is importarit that the strength of thedetergent solution be maintained within relatively close limitsi forwashing milk cans and the like and also for washing milk bottles, andwhile the particular construction set forth in the accompanying drawingsand description is suited more especially for use with machines forwashing milk cans and the like, it is understood that the constructionshown in the drawings may, with slight modifications and within acoverage of the here-- inafter claims, he used for maintaining therequired detergent strength in machines for washing milk bottles and thelike.

As a solution becomes more acid or more alkaline its specificconductance increases, and consequently an electric current passingbetween two electrodes placed in such asolution will vary in the samemanner and can be used to control valves or equivalent feed devices tofeed a concentrated detergent when the detergentjn the wash solutionfalls below a predetermined con-- centration and to stop the feed ofsuch concentrated detergent when the strength of the wash;

solution has been restored to the desired level.

In precision instruments for measuring conductance, in order to avoidpolarization of the electrodes, alternating current up to 1000 or morecycles per second can be employed, and in the present application cyclesper second is preferred, the weak current passing through the to havebeen difficulties, such as fouling of the electrodes, which haveprevented the practical use of such devices in dairies for controllingthe alkalinity or acidity of wash solutions close enough to meet theabove requirements of the New York City Board of Health. Thus, where aconductance cell has been employed it has been submerged in the solutiontank and much trouble has been experienced due to depositsforming on thesurfaces of the electrodes which were usually left in the tank untillong after they ceased to perform their function correctly.

Moreover, the alkalinity or acidity of the solution is not the onlyfactor which determines its electrical conductivity. cream can washingproceeds the washing solution picks up neutral or foreign salts,notablysodium lactate and sodiun acetate which progres'-- sivelyincrease the electrical conductivity of the washing solution and henceact in the same man-t ner as if increases in the alkaline detergent hadvThus, as the milk or.

been made. The present invention therefore also provides anapproximately accurate compensation for these neutral or foreign saltadditions so that a true detergent concentration is maintained at alltimes.

It is accordingly one of the principal objects of the invention toprovide a sensitive control responsive to the electrical conductivity ofa washing solution for overcoming the above disadvantages and formaintaining the conductivity of the wash solution within close limits,the control including an electronic circuit under control of aconductance cell and in" turn progressively incrementing additionsofconcen-- trated detergent for maintaining the active detergentstrength of the washing solution within the required limits.

Another object is to provide such a control in which the electrodes arenot subject to being- 20 invention" providing a moving stream.ofstrained; wash: solution pastthe electrodes and which areafouled bydeposits forming thereon, the present readily removable. The electrodeshave been found to function. properly for. very long periods with-1'alternating current ofnot less. than 69 cycles per second provided theelectrodes are exposed to a moving stream of wash solution fromwhichparticles'i'n suspension have been previously strainediout andfurther provided they are. at alltimes preventedfrom dryingbysubmersion-in a. vessel: of: clean. water: when: not inuse.

Another obiect 'is-ta provide such-:a control: in

which thezelectrodes can be readily removed from: the apparatus 'for theabove mentioned purpose: and in which the strainer can also be readilyremoved for. removing: the particles in suspension.-

Another aim isto provide such a control'in which theoperator isconstantly apprised of thecondition: ofoperationgof the control and alsois warned and the washer rendered inoperativeunless the detergentsolution is up to the required minimum limit of concentration.

Another object is to provide such a control which is free from criticalattenton and supervision and which is automatically out into and outofservice when the can washer is placed in use and shut down.

Another object is to provide such a control in which any failure, as theburning out of a thermionic tube, relay or transformer. will giveawarningsignal and/or-shut down the washer.

Another aim is to provide such a controlwhich can'readily be set to suitany-of the-various de-v tergents-on the market and maintainthedesiredconcentration but which is free from other; adjustments-sothat the apparatus can be readily serviced.

Another object isto provide such a control which is simplegandrugged invconstruction and reliable in: operation so-that it will stand up underrconditionsaof severe and. constant use without.requiringre-adjustment or repairs.

Another-object istoprovide a simple and effective-devicefor-compensating for the addition of salts other thanthe detergent, theaddition of'such foreign salts taking place incident to thewashingioperation.

Other: objects and advantages of the invention willlbe apparent fromthefollowing; description and drawings inwhich:

Fig; 1 is-adiagrammatic side elevational representationof a regulatorresponsive to the electrical conductivity of the wash solution of a milkcan washer or the like and feeding a concentrated detergent solution tothe wash solution to maintain its detergent strength within closelimits.

Fig. 2 is an enlarged vertical section partly in elevation, of theconductance cell and its housing and forming part of the control shownin Fig. 1, this section being taken on line 2-2, Fig. 1.

Fig. 3 is a vertical transverse section through the compensator shown inFig. 1.

Fig. 4 is a vertical fore and aft section through the;. compensatorshown in Figs. 1 and 3, this sectiombeing taken generally on line 4-4,Fig, 3.

Fig; 5* is awiring diagram showing the electricalconnections. betweenthe various components of the control andthe stop button circuit of thedrive motorand how electrical energy is provided when the pump motor isswitched: on.

The. regulator; forming; the. subject. of; the. present". invention. is.designed. to be: used. in. con:

from: the. sump or. tank :at-the. bottom-.of the washer through theusual. pressure'sprays and.

also supplies-a stream: of. thewashing solution for control purposes,andthe; washer. is' shown as having a stop button 8 for the drive motor(not-shown) which drive: motor-'activatesrthe movable parts ofthe-washer...

A part; of the spray water-orwashing" solution circulated; byrthepumpmotor: 5: is .admitedunder; pump. pressurezto; an. inlet pipe.- lflr'of'the.

housing a of; a; conductance cell; indicatedxgenorally at. H, thisconductance cellzand: inletpipe. being carrisi-by. a. supporting plate.12. through; which; the. inlet. pipe: l0; extends and to which it is.secured by-apair or 1111125113 onthe pipe I0 engaging oppositesides .of:the supporting plate l2-.. The inlet pipe lfl-is-shown as having acheckvalve M which prevents reverse flow of the washing solution.

The'conductance cell housing 9 isshown-as including a verticalcylindrical-body [5 having an upper end head 16. brazed or; securedthereon in any. suitable manner and having a bottom or. lower'end head.It detachably securedto. itslower, endand; capable. ofready removal to.permit re-. moval. of; a. strainer screenztherein. Flor-this.- purposethe lower. endhead or bottom It is. PRO-5 vided onits upper; face.withaan. annular groove housing an annular'gasket 19 against which thelower: extremity-of the cylindrical body I5 seats and the lower end heador bottom. I8 is provided with opposite, radially extending bifurcatedears 20 adapted toreceivethe threaded'ends of swing bolts-.2] whichare-hung-upon pins 22 carried by the cylindrical body I5 and carry wingnuts 23 which tighten against the undersides of the ears extension 25 ofthe upper end head l6 enterin the upper end of this cylindrical screenand by a cylindrical extension 26 rising from the lower head or bottoml8. The upper end head I9 is provided with a coaxial through bore 28leading to the space within the cylindrical screen 24 and in this boreis slidably and removably fitted a cylindrical shell 29 of dielectricmaterial, the lower open end of which is spaced from the bottom or lowerend head |B of the body and the upper end of which extends through theupper end head Hi and has a cylindrical dielectric plug 39 fittedtherein. The periphery of the cylindrical plug 39 is provided with oneor more axial grooves 3| which establish communication between thechamber within the dielectric shell 29 and a chamber provided by acylindrical body 32 brazed or otherwise secured to and extendingcoaxially upwardly from the upper end of the housing 9 for theconductance cell.

This cylindrical body 32 is provided with an upper readily removable endhead 33, a gasket 34 being interposed between this cylindrical body andupper end head and this upper end head being removably clamped down by apair of swing bolts 35 carried by pins 36 secured to the cylindricalbody 32 and having their threaded ends arranged to enter bifurcated cars38 projecting radially from the upper end head 33, these swing boltsbeing provided with wing nuts 39 adapted to bear downwardly on thebifurcated ears 38.

The upper part of the axially channeled plug 30 is of tapered form, asindicated at 40, and is fitted into a plug 4| which is in turn screwedinto the upper end head 33. The axially channeled plug 30 is alsoprovided above its tapering part 49, with a flexible two-wire cable 42housing two wires 43 and 44. To provide a watertight seal between theplug 4| and the tapered part 40 of the plug 30, the upper part of theplug 4| is shown as provided with a conical recess containing a conicalfollower 47 of soft, resilient, plastic material, this follower beingexpansively forced into its conical recess by a screw cap on the plug 4|or in any other suitable manner.

One of the wires 43 connects with an electrode or probe 45 extendingdownwardly from the axially channeled plug 39 and exposed to the streamof wash solution flowing upwardly through the dielectric sleeve 29 andthe other of these wires connects with an electrode or probe 46extending downwardly through a dielectric sheath 48 from the plug 36 andalso having its lower end exposed to the stream of wash solution flowingupwardly through the dielectric sleeve 29. It will be seen that theconductance cell assembly comprising the electrodes 45, 46, axiallychanneled plug 39, dielectric sleeve 29, flexible cable 42, plug 4| andupper end head 33 can be readily removed by the simple expedient ofloosening the wing nuts 39 and swinging the swing bolts 35 outwardy.This permits the conductance cell unit, including its electrodes 45 and46 to be removed between washing periods and kept in clean water toprevent fouling of the same.

end 50 of a drain pipe 5|, the horizontal run of which extends throughthe supporting plate I 2 and is fastened thereto by a pair of nuts 52embracing opposite sides of this supporting plate. The drain pipe 5| candrain back into the milk can washer in any suitable manner.

An outlet pipe 55 connects with the side of the upper cylindrical body32 and extends downwardy into a solution feeder or generating tank 56,this pipe 55 terminating in a horizontal run 58 extending along thebottom of the solution feeder tank. The outlet pipe 55 is shown ashaving a hand valve 59 but essentially is provided with a normallyclosed solenoid valve 60, the leads to which are indicated at 6| and 62.The outlet pipe 55 extends through the supporting plate l2 and'isfastened thereto by a pair of nuts 63 tightening against opposite sidesof the supporting plate. A green light 64 is arranged across the lines6| and 62 of the solenoid valve 60 so as to be illuminated when thissolenoid valve is operative.

The solution feed or generating tank 56 is shown as provided above thehorizontal end 58 of the washing solution outlet pipe 55 with ahorizontal foraminous partition 65 adapted to support a quantity of thedetergent in solid form in the upper part of this tank. Above this bedof solid detergent the tank 56 is provided with an overflow 66 which candrain back into the milk can washer in any suitable manner. It will beseen that the depleted wash solution passing upwardly from'the pipe 58through the bed of solid detergent supported on the foraminous partition65 in the solution feed or generating tank 56 takes a portion of thesolid detergent into solution and overflows at 66 back into the washingsolution system of the can washer. The solid detergent in the tank 56can be in the form of powder, lumps or briquets. The acid detergentsused are in liquid form and for such acid detergents the form of thefeeder is necessarily modified.

The electrode wire 43 from the electrode 45 connects directly with anelectronic control circuit contained within a control casing 68 shown inFig. 1. The electrode wire 44 connects with a compensator indicatedgenerally at 69, this compensator being in turn connected through theWire 19 with the electronic control circuit contained within the casing68, Fig. 1. This compensator 69 is for the purpose of compensating forthe neutral salts foreign to the detergent which are added to thesolution as the can washing operation proceeds and will be laterdescribed in detail.

The electronic control circuit is essentially a balanced bridgeresponsive to changes in voltage drop across the wash solution betweenthe elec trodes 45 and 46, an amplifier for the voltage changes of thebridge, and differential relays actuated by the amplifier output and inturn actuating the solenoid valve 60 to control the additions ofconcentrated detergent to the wash solution and also rendering the drivemotorof the can washer inoperative so that the operator can only use thewasher when the detergent is present in the wash solution in the minimumamount called for by the setting of the control. The control circuitalso operates signals, such as light or sound signals, or both, to showthe condition of operation of the control.

The input to the amplifier is a balanced bridge circuit comprising avariable resistor 10 adjusted by a calibrated knob and pointer II on thefront face or panel of the casing 68 (Fig. 1) and havingzonezendxconnect dit on ofthese ondarywindings 12 of a-transformer13,-the primary windine ,14. of-which: isconnected across the load lines.15 and IS- of-the-threephase pump motort. This -transform er I3supplies alternating current for the operation of thecontrol circuit,and hence it will be-seen that the-control circuit is only opera- .tivewhen the pump motor 6 is operative and that ion shut down of thispumpmotor-the control circuit is rendered completely inoperative, thisinsuring-that nopartof the-electronic or. control -circuit is left enerizedon shut down of the pump 'gmotor-fi.

,The cthertnd cftheisecondary winding I2 of -.the transformer1l3 isQonnectedto the line 43 f ;the-.- electrode 45 r and :the other roundednd ...the: calib ated variabl :resist r 10 connected lthroughga line 19and compensator 69 with the lineMIof the other electrode, 46. Acentertap of .th secondary ztransformerwind n 12 is nnected, by a wire 80(with the control grid 8 I of a thermionic amplifier tube 82, this beingshown .,as-being a pentode. It will therefore be seen that ;a bridgecircuit is provided, two legs of which are provided by the two halves ofthe secondary winding-1270f the transformer T3, the third leg by ,,thevariable resistor, and thefourth leg by the electrodes 45,49. The powerinput to this bridge .isacross the secondary-winding l2'which forms vtwoofits legs and the grid 8| of the amplifier ,tube is connected to thecorner of the bridge between these legs, the opposite corner beinggrounded. Accordingly, any change in conductance of the leg containingthe electrodes 45, 46 upsets the balance of thebridge. and impresses asignalvoltageon the grid.8I of the amplifier tube 82.

Theplate 90 ofthis amplifier tube 82 is conv nectedtosa wire 9I which isconnected through a resistor 95 with the control grid ,92 of athermipnic vacuum tube 93for a relay 94 and directly, with the controlgrid- 96 of a thermionic-vacuum tube 98 for a relay 99. The platecircuit of the amplifier tube32 is completed through a resistor I00.connected with the grid end of the resistor 95 .and wire IOI connectingwith the center tap of a secondary winding I02 of the transformer 13. Apair of resistors I03 and I94 are connected in series from this centertap wire to one end I09 ,of this secondary winding I02 of thetransformer 73 and a wire I06 connects the midpoint of these {resistorsI03, I04 to the grounded end of a variable .resistor I07. The movablecontact I08 of this variable resistor I91 is connected by a wire I09with the cathode I I0 of the amplifier tube 82 and also with itssuppressor grid III, this variable resistor I01 thereby controllingthe-grid bias of the amplifier tube 32. The screen grid II2 of theamplifier tube 82 is connected with the transformer-center tap wire IOIand a bypass condenser II3 is provided between the plate and .screengrid.

It will be seen that plate current of the ampli' fier tube 82 passesthrough the plate 90, wire SI, resistors 95 and I00, center tap wireIOI, lower ,half of the secondary transformer winding I02, ,resistorI04, wire I06, variable resistor I91 and wire I09 to the cathode H0. Itwill also be seen that a differential in potential impressed on the.control grids 92 and 9B of the relay vacuum tubes 93 and 98,respectively, is obtained through the resistor 95.

The plate II5 of the relay tube 98 is connected by a .wire II6 with thewinding II8 of its relay gg the otherl end' of;t hi s winding beingconnected .toawire I I9- leading to the end-of the secondary,transformer winding I02 opposite its side I05.

mally closed solenoid valve 60 thereby to permit this .valve to-closeand out off the fiow of wash solution'through the regenerating or feedertank .56.

The plate I25 of the ;relay tube 93 is connected by awi e I26withzthewinding I28 of its-relay 94, the other end of this winding beingconnected to the wire 'I I9 leading to the end of the second arytransformer winding I02 opposite its side I05.

This relay has two mechanically connected movablecontacts I29 and I30insulated from each other, thecontact I29 being connected by a'wire I'3Iwith the load line I5 of the pump motor 6. The movablecontact I29 isnormally closedor in engagement with the fixed contact I32 of a line I33connecting with the load line 16 of the pump motor 6 and-containing ared warning light or signal I35 which can also be in the form of.anaudible signal. 'Ihemovable contact I30-is normally open with-referenceto its-fixed contact I36,-the. contacts being in circuit through wiresI31 and I38- with the stop button 8 of the starter forithe drive motor(not shown), this drive motor actuating the mechanically moving parts ofthe washer. When the winding I28 of the relay'94 issuflicientlyenergized the normally openmovable contact I30 is pulled up into engaement with the fixed contact I36 tocomplete the stop .button'circuit 8of the drive motor for the milk can washer and render it operative. Atthe same t me the movable contact'l29 is pulled away from its fixedcontact I32 to de-energize the red warning light or signal I35. Thereverse takes place when the conductivity of the wash solution fallstea-predetermined danger level, the coil I38 of the relay 94 beingeffectively tie-energized, the red warning signal I35 being energizedand the can washer drive motor stopped by breaking the circuit throughits starter 8.

As the washing of the cans proceeds, salts other than the detergentprogressively build up in the washing solution. "These neutral orforeign salts, of course, increase the electrical conductivity of thewashing solution-and-since the controlof-the detergent additions in thepractice of the present invention is in response to the electricalconductivity of the washing solution, it is apparent that unlesscompensation is made for the building up of such foreign salts,inadequate additions of the detergent-would be made as the can or bottlewashing proceeded, the control not distinguishing between the increasedconductivity provided by the detergent additions and the increasedconductivity provided by the gradual accumulation of foreign salts. Tocompensate for such gradual accumulation of foreign salts, thecompensator I59 is provided across the solenoid valve 50 and which canbe constructed as follows:

The numeral I45 represents a rectangularcas- -ing having a vertical backwall I45 and a removable front wall I48. Within this casing is suit-.ably secured a, vertical partition I49 arranged parallel with the frontand-rear walls I46 and the lines 44 and 19 for this purpose.

the moving parts of the compensator. A solenoid I50 is secured to thefront face of this partition at one end thereof with its axially movablecore II projecting toward the opposite end of the partition. This coreI5I is normally retracted from the winding of the solenoid by a helicalcompression spring I52 anchored on a bracket I53 which can be adjustablysecured to the front face of the partition I49 by screws I54; the axialmovement of the core against the resistance of this spring I52 beingeffected by the energization of the solenoid. For this purpose one endof the winding of the solenoid I50 is connected with the load line 16 ofthe pump motor 6 and the other end of the winding of the solenoid I50 isconnected by a line I55 with the other line 6| of this solenoid valve60. It will therefore be seen that the solenoid I50 is connected inparallel across the solenoid valve 60 and that every time this solenoidvalve 60 is actuated the solenoid I50 is energized.

Above themovable core I5I of the solenoid I50, a bushing I56 is mountedin the partition I49 to project axially forwardly therefrom, thisbushing .being shown as having a reduced threaded neck extending throughthe partition I49 and secured by a lock nut -l58. In this bushing isjournalled a shaft I59 which projects forwardly through an opening inthe removable front wall I48 of the casing and is provided with a handknob 160 by means of which the shaft I59 can be manually .tumed to zero,this hand knob being shown as having an arrow for this Purpose and whichis adapted to be brought into register with a zero mark on the frontwall I48 of the compensator casing. The rear end of this shaft I59 iscon- .non-rotative relation to the partition I49 by a supporting pin I63on which the rheostat casing is slidingly mounted and which is in turnfixed to the partition I49 by a screw I64. This rheostat is connected inone of the lines to the conductivity cel1 II, it being shown asconnected to It functions progressively to cut resistance into theconductivity cell circuit to compensate for the increased conductivityoccurring through the building up of neutral or foreign salts in thewashing solution. A second rheostat I61 is shown (Fig. 5)

as connected in parallel with therheostat [SI for adjustment purposes.

A thrust washer I65 is arranged on the shaft I59 in advance of thebushing I56 and in advance of this thrust washer is arranged a bearingbushing I66 which is loose on the shaft I59 and which carries a ratchetwheel I68 which can also be loose thereon. On this bearing bushing I66is also journalled the end of a depending arm I69, the free end of whichis slotted as indicated at I and connected by a pin I1I to the core ofthe solenoid I50 so that the arm I69 is oscillated about the axis of theshaft I59 each time the solenoid I50 is energized.

As best shown in Fig. 3, this arm I69 has pivoted thereto a pawl I12,the tooth of which is urged into engagement with the teeth of theratchet wheel I68 by a small spring I13 between the pawl and its armI69. The teeth of this ratchet wheel are also engaged by a holding dogI14 pivoted on the partition I49 and having its tooth urged intoengagement with the teeth of the ratchet wheel I68 by a small spring Ibetween the holding dog and the partition I49. It will be seen that eachtime the solenoid I50 is energized to oscillate the arm I69 to theright, as viewed in Fig. 3, the pawl I12 is drawn along the teeth of theratchet wheel I68 to engage a subsequent tooth thereof, retrogrademovement of the ratchet wheel I88 being prevented by the holding dogI14. Each time the solenoid I50 is de-energized the spring I52 draws thesolenoid core I5I and arm I69 to the left, as viewed in Fig. 3, thereby,through the pawl I12, to impart a partial clockwise rotation to theratchet wheel I68. The ratchet wheel I68 is thereby advanced step-bystepas the solenoid I50 is energized and deenergized.

This step-by-step advance of the ratchet wheel I68 is transmitted to therheostat I6I by a friction clutch which is shown as comprising a disk518 on the shaft I59 in advance of the ratchet wheel I68 and as havingits hub secured to this shaft by a set screw I19 or in any othersuitable manner. A friction ring I of any suitable frictional materialis shown as secured totherear face of this disk I18 by screws I8I and asengaging the forward face of the ratchet wheel I68. The frictionalcontact between this friction ring I80 and the ratchet wheel I68 isdetermined by a helical compression spring I83 surrounding the shaft I59and interposed between the partition I49 and rheostat casing I62. Itwill be seen that this friction clutch permits the rheostat I 6 If to.be set to zero after each shutdown of thewashing machine. Thus therheostat is advanced step-by-step by the solenoid I50 to cut resistanceinto the conductivity cell II circuit as the washing proceeds tocompensate for neutral or'foreign salt additions. When the washer isshut down the operator turns the knob I60=and shaft I59 to reset therheostat I6l to zero, this being permitted by the friction clutchengagement between the friction ring I80 and the ratchet wheel I68. I

Operation tion in its spray system has an activealk'alinity of 0.04%,this being below the range which-the control is set to maintain.

The operator places the spray jets of the washer in operation bystarting the three-phase pump motor 6 (Fig. 5) through its starter 1.This, through the pump motor loadlines15 and 16 energizes the electroniccontrol circuit and also pumps washing solution into the inlet pipe .I0(Fig. 1) of the conductance cell housing II.

This washing solution from the inlet pipe I0 passes the check valve I4into the lower cylindrical body I5 of the conductance cell housing. Inthis lower cylindrical body (Fi 2) this stream of washing solutionpasses through the-cylindrical screen 24 and through the lower open endof the dielectric sleeve 29 upwardly through this sleeve and past theexposed electrodes 45 and 46, escaping through the axial grooves 3| inthe dielectric plug 30 into the upper cylindrical body 32. From thisupper cylindrical body this stream of washing solution spills from thenozzle 49 into the upstanding end 50 of the drain pipe 5| which returnsthe washing solution to the can or bottle washer.

Referring to Fig. 5, it will be-seen that the contacts of the relay 94are normally in the position shown with its contact I29 closed and henceon so starting the pump motor 6 with a substandard detergentconcentration, the red light I35 is illuminated, this red light beingenergized by cur rent supplied from the load line I5 of the pump motor6, wire I 3|, closed contact I29 and fixed contact I32 of relay 94, wireI33 and red light I35 to the other load line I6 of the pump motor 6.This red light shows that the can washer is not yet in condition forfull operation. It will also be seen that the relay 94 prevents thedrive motor (not shown) from starting at this time. Thus, in this normalor effectively de-energized condition of this relay 94 its contacts I30and I36 are open sothat the circuit through the stop button circuit 8 ofthe drive motor is open.

Referring again to Fig. 5, it will be seen that therelay 99 is normallyclosed and hence on so starting the pump motor 6 with a substandarddetergent concentration, the normally closed solenoid valve 60 isopened, this normally closed solenoid valve being energized by currentsuppliedfrom the load line I5 of the pump motor, closed contact I20 ofthe effectively deenergized relay 99, fixed-contact I2I, wire 6|,solenoid valve 60 and wire 62 to the other load line I6 of the pumpmotor 6. At the same time the green light 64 in parallel with thesolenoid valve 60 is illuminated to indicate that the solenoid valve 60-is open and operating.

With the solenoid valve 60 so open a part of the washing solutionentering at the pipe I passes to the upper cylindrical body 32 (Fig. 2),escapes through the pipe 55 (Fig. 1) and past the open solenoid valve 60and hand valve 59 into=the space inthe feeder tank 56 below itsforaminous partition 65. This dilute solution flows upwardly through thebed of solid alkaline detergent, in briquet, granular or powder form,supported on the foraminous partition 65 and escapes through theoverflow 66 and returns to the spray section of the can washer. In soflowing upwardly through the bed of solid alkaline detergent on theforaminous partition 65, the dilute washing solution dissolves a part ofthe solid detergent and hence is fortified or strengthened in itsdetergent component. This results, of course, in a steady increase indetergent strength and alkalinity of the washing solutionbeinglcirculated by the pump driven by the motor Gas just described.'

At the assumed start of operation, energization of the load lines I and16 (Fig. 5) of the threephase pump motor 6 energizes the primary windingI4 of the transformer I3 and hence also energizes its secondary windingsI2 and I02. This secondary winding 12 forms two legs of a bridge, theother two legs of which contain, respectively, the variable resistor I0and the electrodes or probes 45 and 46. together with the compensator69. The potential impressed upon the'bridge by the secondary winding I2is thereby impressed across the variable resistor I0 and, through theWireIQ, rheostats ISI and I6! of the compensator 69 and wire 44 acrossthe electrodes 45 and 46 of the conductance cell II, the electrode 45connecting with the winding I2. The variable resistor I0 has beenassumed to have been set to maintain the desired operating point and asit is also assumed that the wash solution passing the electrodes 45 and46 is below strength, the bridge is unbalanced and hence a potential isimpressed on the control grid '8I of'the amplifiertube'82-to' renderthis tube conductive.

Since the solfibi'd" valve 60 is open, concentrated detergent is beingadded to the washsolution and-its conductance is increasing, thistending to bring the bridge to the balance determined by the setting ofthe variable resistor I0. When the active alkalinity of the washsolution increases to 0.065%, 1. e. the setting of the variable resistorI0, the bridge is brought to balance and the potential on the controlgrid 8| of the amplifier tube 82 reduced to its cutoff point to renderit nonconductive.

The plate potential for the amplifier tube 82 is supplied by the lowersection of the secondary winding I 92 of the transformer I3, the platecurrent passing-from the plate through wire 9|, resistors and I89, wireIOI,' lower section of the secondary winding I02 and-resistors I04 andI03to wire I 06, bias resistor I0! and wire I09 to the cathode H0." Therelay tubes 93 and 98 have the same characteristics and since thecontrol grid 92 of the relay tube 93 is connected through the resistor95 withthe plate 90 of the amplifier tube 82 it is at a lower negativebias than the grid-96 of the relay tube 98 so that on rising values ofplate current from the amplifier tube 82 the relay tube 98 becomesconductive before the relay tube 98. In practice, these relay tubes 93and 98 are conductive under all conditions of operation, their relaysbeing selected to cutin and out at predetermined'platecurrent values.

The plate potential for the relay tubes 93-and 98- is supplied by theupper section of the secondary winding I02 of the transformer I3. Whenthe relay tube 93 becomes eifctively operative its plate current passesthrough and effectively energizes the winding I28-of its relay 94. Thisopens its contacts I29 and I32and thereby extinguishes the red light I35in circuit therewith, this informing the operator that'he can start themain motor '(not shown) of the washer. This condition is obtainedthrough the-closing of the other two contacts I30; I36 ofthe relay 94and which closes the circuit through the stop button circuit 8 ofthedrive motor starter.

The solenoid valve at this time is still open and hence detergent'isstill being added to the wash solution. It is important that thealkalinity of the wash solution does-not exceed a predeterminedvalue,this being assumed to be 0.08% active-alkalinity. As the wash solutionapproaches this maximum active alkalinity value the plate current fromthe amplifier tube 82 also rises and when this value is reached, thepotential impressed on the control grid 96 of the relay tube 98 is abovethe cut off point of this relay tube so that this relay tube is renderedeffectively conductive. With this relay tube 98 effectively conductiveits plate current flowing through the winding I I8 of its relay 99elfectively energizes this relay. This pulls up its contact I28 so as tobreak the circuit through the normally closed solenoid valve 60 andgreen light 64 in parallel therewith. With the solenoid valve 60 closedthe flow of wash solution'through' the feeder tank 56 is-cut 01f so thatdetergent additions to the washing solution are cut off.

As the washing of the cans or bottles proceeds the concentration ofdetergent in the washing solution diminishes both through the functionof the detergent in cleaning the cans and also through a part of thewashing solution clinging to the cans, make-up water being supplied.When the concentration of the washsolution drops to 0.065% activealkalinity, the increasing negative potential impressed on the controlgrid 8| of the amplifier tube 82 by the unbalancing of the bridgethrough the resistance provided by the washing solution passing theelectrodes 45 and 46 in one of its legs causes such decreased value ofplate current from the amplifier tube 82 that the potential impressed onthe control grid 95 of the relay tube 98 is reduced to a point where theplate current from this relay tube 98 is insufiicient to hold the relay99 efiectively energized. The effective deenerglzation of this normallyclosed relay 99 causes its movable contact I20 to re-engage the fixedcontact I2I and hence re-establish a circuit through the normally closedsolenoid valve 60 and its green light 54. This opens the solenoid valve60 so as to re-establish a flow of washing solution through the feedertank 59 thereby to add to the detergent content of the washingsolution'from the solid alkaline detergent contained in the feeder tank59.

It will be seen that each time the active alkalinity of the washsolution reaches the assumed 0.08% the relay tube 98 and its relay 99are rendered operative to de-energize the normally closed solenoid valve60 and its green light '04 and cut ofi detergent addition to the washwater and that each time the active alkalinity of the washing solutiondrops to the assumed 0.065% the relay 99 is effectively deenergized toenergize the normally closed solenoid valve 60 and its green light 64and start the addition of detergent to the washing solution.Accordingly, the washing solution is maintained at an active alkalinityof from 0.065% to 0.08% by the successive opening and closing of thesolenoid valve 60 in response to the changing conductivity of the washsolution.

' As the wash operation proceeds neutral or foreign salts form andaccumulate in the washing solution. Where milk cans are being washedsuch neutral salts are principally in the form of sodium lactate andsodium acetate. The electrodes 45, 46 are, of course, unable todistinguish between the increased conductivity provided by such neutralsalts as compared with the alkaline detergent and hence, in the absenceof compensation for the accumulation of such neutral salts the washingsolution would progressively be fed less and less detergent and thedetergent concentration would fall below the standards which the controlis set to maintain.

In accordance with the present invention increments of resistance areprogressively cut into series with the electrodes 45, 46 so as tocounterbalance the increased conductivity provided by the accumulationof neutral salts. In the practice of the present invention an incrementof resistance is added in series with the electrodes each time thesolenoid valve 60 operates so that the resistance added is in proportionto the use of the detergent. Thus (Fig. each time the solenoid valve 60is energized, the solenoid I50 in parallel therewith is likewiseenergized. This solenoid I50 (Fig. 3) swings the lever I99 to the right,thereby drawing its pawl I12 along the teeth of the ratchet wheel I68,corresponding movement of this ratchet wheel being prevented by theholding dog I14. When the solenoid I50 is de-energized, its returnspring I52 draws the core I5I and arm I69 to the left as viewed in Fig.3, thereby to advance the ratchet wheel I58 one step. Therefore, eachtime the solenoid valve 00 and solenoid I50 are de-energized, theratchet wheel I68 is advanced one step.

This ratchet wheel is connected through the frictionwhel I18 with theshaft I59 which is turn is connected with the movable contact of the.

rheostat I6I. The resistance of this rheostat is held stationary in itscasing which in turn is prevented from rotating by its mounting on thepin I68 and the direction of movement of the movable contact is such asto add an increasing amount of resistance each time the ratchet wheelI68 is advanced one step. This rheostat IBI is in series with one of theleads from'the conductivity cell II and hence it will be seen that thisresistance is added to the electrode circuit to compensate for theaccumulation of neutral salts.

On shutdown, when the operator de-energizes the three-phase pump motor6, he likewise deenergizes the entire electronic control circuitinasmuch as this electronic control circuit is across two of the loadlines of this three-phase pump motor. It will therefore be seen that onshutdown of the washer there is no danger of leaving any part of thecontrol circuit energized and no special switch is therefore requiredfor the control circuit.

the operator restoresthe knob I00 (Fig. 1) to its zero position. Turningthis knob, which is fast to the shaft I59, re-sets the rheostat I6I tothe position in which it does not offer any resistance. I Such resettingof the knob does not affect the ratchet mechanism mounted on the shaftI59 because .of the presence of the friction clutch ring I between thefriction wheel I18 fast to the shaft I59 (Fig. 4) and the ratchet wheelI58. The apparatus is now in the condition'assume'd at the start of theoperation and ready for reuse as described.

From the foregoing it will be seen that the present invention provides avery simple and accurate control for maintainingthe detergent strengthof a washing solution within close limits and which will stand up underconditions of severe and constant operation without getting out of orderand requiring servicing. ,Fur-

ther, adequate compensation is made for the accumulation of neutralsalts in the washing solution, particularly where cans are unusuallydirty and the detergent is used up faster and the feeding periods arespaced at shorter intervals and more increments of resistance are addedin a given time to compensate for the extra neutral salts being formed.It will also be seen that with the forced flow of a small screenedstream of the washing solution through the conductivity cell II and withthe form of this cell there is little danger of this cell fouling up andrendering the control inoperative. Further, the screen 24 can be readilyremoved for cleaning and the electrode assembly, including the removablehead 33 and flexible cable 42, can likewise be readily removed so thatthe electrodes can be stored in clean water during shutdown periods ofthe washer.

By warning signal as used in the appended claims is meant to include theshutting down of the washer itself through the energization of this maindrive motor, such automatic shutdown of the washer operating, of course,as a very pointed warning to the operator that conditions should berectified.

I claim: 7

1. A regulator for restoring the specific electrical conductance of asolution maintained at a predetermined temperature, whenever a smallreduction in conductivity occurs, which comprises a feeder arranged toadd to said solution a concentrated'component thereof, 'means providingAlso, on emptying wash tank.

assume an-electricalcurrent'in excess of a predetermined value andvarying in response to changes :in conductivityof said solution, a'pairof parallelelectrical circuits energized by said electrical currentslightly below said low value and inoperative when said conductivity israised-to said low value, 'and means in circuit with'said switch opened'in response to said high value of conductivity and arranged to rendersaid feeder operative -when.

said-conductivity falls toa level slightly below said high "value andarranged to render said feeder inoperative when said conductivity isrestored to said high value,--whereby the conductivity of saidsolution'is maintained substantially constant.

'2. A regulator for restoring the .specific electrical conductance -of-asolution'maintained at 'a predetermined temperature,- whenever a smallreduction inconductivity-occursnvhichcomprises a "feeder arranged to addto "said solution a concentrated component thereon-means providingan'electrical current in-excess of a'predetermined value and varying inresponse-to changes in conductivity of said solution;a pairof-parallelelectrical circuits energized by said electrical current varying meansto respond to'the variations of said electrical current andone-actuatinga normally closed switch closed in response to a low valueof conductivity of said solution-and the other actuating a switch openedin'response to a high value of conductivity of said solution, a warningsignal in circuit with and rendered operative by the closing of saidnormally closed switch when said-conductivity falls slightly below saidlow value and inoperative when said conductivity is raised to said low-value, and means in circuit with said switch openedin response to ahigh value of conductivity and arranged to render said feeder operativewhen said conductivity falls to a level slightly below said high valueand arranged to render said feeder inoperative when said conductivity isrestored to said high value, whereby the conductivity of said solutionis maintained substantially constant.

'3. A regulator for restoring the electrical conductivity of a solutionmaintained at a predetermined temperature, whenever alsmall reduction inconductivity occurs, which comprises-a feeder arranged to add tosaidsolution :a con centrated component thereof, :a pair of electrodesimmersed in said solution, means arranged to pass a current through saidelectrodes and through the solution therebetween, a pair of parallelelectrical circuits energized in response to small changes in voltagedropin excess of a. predetermined value across the solution between saidelectrodes and one actuating-a firstrswitch rendered operative inresponse to a high level in said voltage drop and the other actuating :asecond switch rendered operative in response to a low level of saidvoltage drop, a warning means, means in circuit with said first switchand arranged to render said feeder operative when said voltage .dropsslightly -:below said :high .level and arranged to render :feederinoperative when :said voltage is'restored to said high level wherebythe conductivity of said solution is maintained substantially constant,and means'in circuit with said second switch and arranged to render saidwarning means operative when said voltage falls slightly below said lowlevel and inoperative when said voltage is raised to low level.

4. A regulator for restoring the specific electrical conductance of asolution maintained at a predetermined temperature, whenever a smallreduction inconductivity occurs, which comprises a feeder arranged toadd to said solution a concentrated component thereof, a pair ofparallel electrical circuits each including the cathode, grid and plateof a thermionic vacuum tube and the winding of a relay actuated inresponse to a predetermined level of the plate current thereof, meansbiasing said grids to provide different plate current levels in responseto the same source :of grid potential, means providing an electricalcurrent varying in voltage in excess of a predetermined .value inresponse to-changes inconductivity of said solution in excess of apredetermined valueand providing said source of grid potential, awarning means, means in circuit with the contactsof the relay having itswinding in :the circuit maintained at a lower level of plate current,and arranged to render said feeder 0perative when the plate current inthe circuit maintained at-alower level of plate current drops slightlybelow its said predetermined level and arranged-to-render said feederinoperative when the plate current in the circuit maintained at a lowerlevel of plate current is restored to its said predetermined ,level, andmeans in circuit .with the contacts of -,-the relay having its windingin circuit with-the-circuit maintained at a .higher level of platecurrent and arranged to render said warning means operative when theplate current in the circuit maintained at a higher level of platecurrent falls slightly below its said predetermined level andinoperative when the plate current in the circuit maintained at a higherlevel of plate current is raised to its said predeterminedlevel.

5. A regulator for restoring the specific electrical conductance of asolution maintained at a predetermined temperature, whenever a smallreduction in conductivity occurs, which comprises a feeder arranged toadd to said solution a concentrated component thereof, electrodesimmersedin said solution, a pair of parallel electrical circuits eachincluding the cathode, grid and plate of a thermionic vacuum tube andthe winding of'a relay actuated in response to a predetermined-level ofthe plate current thereof, means biasing said grids to provide differentplate-current levels inresponse to the same source of grid potential, anamplifier including a thermionic vacuum tube in circuit with saidelectrodes and responsive to small changes in voltage drop in-excess ofa predetermined value across the solution therebetween and providingsaid source of gridpotential, a warning means, means in circuit-with thecontacts of the relay having its winding in the circuit maintained at alower level of plate current, and arranged to render said feederoperative when the plate current in the circuit maintained at a lowerlevel of plate current drops slightly below its said predetermined leveland arranged to render said feeder inoperative when the plate current inthe circuit maintained at a lower level of plate current :is restored toits said predetermined level, and means in with the contacts of the:relay having its winding in circuit with the circuit maintainedatahigher level of plate current and arranged to render said warning meansoperative when the plate current in the circuit maintained at a higherlevel of plate current falls slightly below its said predetermined leveland inoperative when the plate current in the circuit maintained at ahigher level of plate current is raised to its said predetermined level.

6. A regulator for maintaining the detergent strength of the washingsolution in a washer having a warning means, which comprises meanspassing an electric current through the washing solution, an amplifierfor said current, a resistor in the output line of said amplifier, afirst control grid of a first thermionic relay tube connected with saidoutput line between said amplifier and said resistor, a second controlgrid of a second thermionic relay tube connected with said output lineon the side of said resistor remote from said amplifier, a first relayenergized by the plate current controlled by said second control gridand arranged, when energized, to deactivate said warning'means, adetergent feeder adapted to feed a concentrated detergent to saidwashing solution, a second relay energized 'by the plate currentcontrolled by said first control grid, and means in circuit with saidsecond relay for rendering said detergent feeder operative when saidsecond relay is deenergized and inoperative when said relay isenergized.

7. A regulator for maintaining the alkaline detergent strength of thewashing solution in a washer having a drive motor magnetic starter witha. stop button circuit,- which regulator comprises means passing anelectric current through the washing solution, an amplifier for saidcurrent, a resistor in the output line of said amphfier, a first controlgrid of a thermionic relay tube connected with said output line betweensaid amplifier and said resistor, a second control grid of a thermionicrelay tube connected with said output line on the side of said resistorremote from said amplifier, a normally closed relay energized by theplate current controlled by said second control grid and arranged. whenenergized, to break said circuit through said drive motor starter, adetergent feeder adapted to feed a concentrated detergent to saidwashing solution, a second normally closed relay energized by the platecurrent controlled by said first control grid, and means in circuit withsaid second relay for rendering said detergent feeder operative whensaid second relay is deenergized and closed.

8. A regulator for maintaining the detergent strength of the washingsolution in a washer having a drive motor magnetic starter with a stopbutton circuit and a warning device, which comprises means passing anelectric current through the washing solution, an amplifier for saidcurrent and providing rising outputvoltage in response to risingelectrical conductivity of said washing solution, a thermionic relaynetwork responsive to a low value of said output voltage below apredetermined value and deenergizing said drive motor starter when saidoutput voltage falls to said low value, a detergent feeder adapted tofeed a concentrated detergent to said washing solution, a secondthermionic relay network re sponsive to a higher value of said outputvoltage, means actuated by said second thermionic relay network 'fordeenergizing said detergent feeder to render it inoperative 'when saidoutput voltage rises to said high value, and means adjustably regulatingthe operating point '01 said amplifier.

9. In a regulator for maintaining the de rgentstrength of the washingsolution in awasher wherein the solution continuously increases inuseless conductive salt accumulations and having a pair of electrodesimmersed in said solution, means passing an electric current throughsaid electrodes and the solution therebetween, an amplifier for saidcurrent, a relay closed by the current, below a predetermined value,from said amplifier, a detergent feeder for feeding, when energized, aconcentrated detergent to said washing solution and means responsive tothe closing of said relay for energizing said detergent feeder when saidcurrent from said amplifier falls to a predetermined level above saidpredetermined value and deenergizing said detergent feeder when saidcurrent from said amplifier rises above said predetermined level wherebythe conductivity of said solution is maintained substantially constant:the combination therewith of a com-' pensator for said uselessconductive salts accu mulating in said washing solution, comprising arheostat in circuit with said electrodes, and means synchronized withthe operation of said relay and successively actuating said rheostat tosuccessively increase the value of its resistance to compensate for thechanging conductance of said washing solution caused by the accumulationof said salts, whereby the detergent strength of salid'solution ismaintained substantially constant.

10. In a regulator for maintaining the detergent strength of the washingsolution in a washer wherein the solution continuously increases inuseless conductive salt accumulations and having a pair of electrodesimmersed in said solution, means passing an electric current throughsaid electrodes and the solution therebetween, an amplifier for saidcurrent, below a predetermined value, a relay closed by the current fromsaid amplifier, a detergent feeder for feeding, when ener ized, aconcentrated detergent to said washing solution and means responsive tothe closing of said relay for energizing said detergentfeeder when saidcurrent from said amplifier falls to a predetermined level above saidvpredetermined value and deenergizing said detergent feeder when saidcurrent from said amplifier rises above said predetermined level wherebythe conductivity of said solution is maintained substantially constant;the combination therewith of a compensator for said useless conductivesalts accumulating in said washing solution, comprising a rheostat incircuit with said electrodes, a solenoid energized by said relay, andmeans actuated by said solenoid, when energized, and progressivelyadvancing said rheostat to progress ively increase the value of itsresistance in circuit with said electrodes to compensate for thechanging conductance of said washing solution caused by the accumulationof said salts, whereby the detergent strength of said solution ismaintained substantially constant.

11. In a .regulator for maintaining the Ge tergent strength of thewashing solution in a washer wherein the solution continuously increasesin useless conductive salt accumulations and having a pair of electrodesimmersed in said solution, means passing an electric current throughsaid electrodes and the solution therebetween, an amplifier for saidcurrent, below a predetermined value, a relay closed by the current f omsaid amplifier, a detergent feeder for feeding, when energized, aconcentrated detergent to said washing solution and means responsive tothe closing of said relay for energizing said detergent feeder when saidcurrent from said amplifier falls to a predetermined level above saidpredetermined value and deenergizing said detergent feeder when saidcurrent from said amplifier rises above said predetermined level wherebythe conductivity of said solution is maintained substantially constant;the combination therewith of a compensator for said useless conductivesalts accumulating in said washing solution, comprising a rheostat incircuit with said electrodes, a solenoid energized by said relay, and aratchet mechanism advancing said rheostat through motion derived fromsaid solenoid, when energized, to progressively increase the value ofits resistance in circuit with said electrodes to compensate for thechanging conductance of said washing solution caused by the accumulationof said salts, whereby the detergent strength of said solution ismaintained substantially constant.

12. A regulator for maintaining the strength of a body of a solutionsubject to depletion of a component which affects the electricalconductivity of said solution, which comprises a conductivity cellhousing, a pair of removable electrodes projecting into said cellhousing, means continuously passing a stream of solution withdrawn fromsaid body through said cell housing,

in contact with said electrodes therein, aconduit returning said streamof solution from said cell housing to said body, a feeder for feeding,when energized, said component tosaid solution, a second conduit adaptedto divert a part of the stream of solution from said cell housing tosaid feeder, a valve in said second conduit, means passing an electriccurrent through said electrodes and the solution therebetweeen, anamplifier for said current, means responsive to changing values of saidamplified current above a predetermined value for energizing said valve'when said current from said amplifier falls to a predetermined levelabove said predetermined value and deenergizing said value when saidcurrent from said amplifier rises above said predetermined level wherebythe conductivity of said solution is maintained substantially constant,and means returning said solution from said feeder to said body.

13. In a regulator for maintaining the strength of a body of a solutionsubject to depletion of a component which affects the electricalconductivity of said solution, a tubular conductivity cell housinghaving end heads at its opposite ends and having and inlet adjacent itsperiphery and an outlet adjacent its axis, a tubular screen removablyarranged coaxially in said housing and dividing said housing into aninner chamber communicating with said outlet and an outer chambersurrounding said inner chamber and communi-- cating with said inlet, anda pair of removably spaced electrodes projecting axially from one endhead of said housing into said inner chamber and immersed in thescreened solution passing therethrough.

14. In a regulator for maintaining the strength of a body of a solutionsubject to depletion of a. component which affects the, electricalconductivity of said solution, a tubular conductivity cell housinghaving an inlet adjacent its periphery and an outlet adjacent its axis,a tubular screen removably arranged coaxially in said housing anddividing said housing into an inner chamber communicating with saidoutlet and an outer chamber surrounding said inner chamber andcommunicating with said inlet, a dielectric sleeve fitted in said outletand projecting axially into opposite end thereof, a dielectric lugfitted in said sleeve and partly closing the same, a pair of spacedelectrodes projecting axially from said plug into said sleeve andimmersed in the screened solution passing therethrough, and meansremovably securing said dielectric plug in said housing.

15. In a regulator for maintaining the strength of a body of a solutionsubject to depletion of a component which affects the electricalconductivity of said solution, a conductivity cell housing including alower tubular body, a coaxial upper tubular body, an intermediatepartition interposed between and secured to said tubular bodies, anupper end head detachably secured to said upper tubular body, a lowerend head detachably secured to said lower tubular body, saidintermediate partition being provided with an axial opening providingcommunication between said tubular bodies and said upper and lowertubular bodies being provided, respectively, with an outlet and aninlet, a dielectric sleeve fitted in said axialopening and projectingaxially into said 'lower tubular body, atubular screen interposedbetween: said intermediate partition and said detachable lower end headand surrounding said sleeve,a tubular dielectric plug passing throughand secured to said detachable upper end head-in line with-said sleeveand fitted in said sleeve and partly closingthe'same and a pair 7 ofelectrodes projecting-=axially from said second plug-intoisaid' sleeveand immersed in the solution passing therethrough.

. 'lfiaAregulator-for restoring the specific electrical conductance of asolution maintained at a predetermined -"temperature, whenever a smallreductionin conductivity occurs, which comprises a feeder arranged toadd to-said solution a concentrated component thereof, electrodesimmersed in said-solution, a-pair of parallel electrical circuits, afirst switch actuated in'response to a predetermined current level inone of said circuits, means in circuit with said electrodes responsiveto small changes in voltage drop in excess of a predetermined valueacross the solution therebetween for adjusting the current level in saidone of said circuits to a lower value, at a given voltage drop betweensaid electrodes, than the current level in the other of said circuits,means in circuit with said first switch arranged to render said feederoperative,-when said current in said one of said circuits drops slightlybelow its said predetermined current level and arranged to render saidfeeder inoperative when said current in said one of said circuits isrestored to its predetermined level, whereby the conductivity of saidsolution is maintained substantially'constant, a second switch actuatedin response to current changes in said-other of said circuits, a warningmeans, and means in circuit with said second switch and warning meansand arranged to render said warning means operative when said ciirrentlevel in said other of said circuits falls slightly below itspredetermined level and inoperative when said current level in saidother of said circuits is raised to its said pre determined level,'o'rwhenever said feeder fails to maintain the conductivity of said solutionsubstantially constant.

17..A regulator for periodically restoringthe detergent'strength of the.washing solution maintained at a predetermined temperature whenever asmall reduction of the detergent strength occurs in a washerhaving anelectric motor driven pump, said pump arranged torecirculate saidwashing solution from a sump containing the main body of said solution,and in addition to provide a small sample stream representative at alltimes of the electrical conductivity and of the detergent strength ofthe solution, a power source for said motor driving said pump, a motorstarter arranged in series between said power source and said motor forcontrolling said motor, a circuit passing a current tapped from a pointbetween said starter and said motor arranged to energize said regulatorupon start of said motor and deenergize same upon shutdown of saidmotor, a conductivity cell housing, and said representative samplestream arranged to pass through said housing and return to said sump, apair of spaced electrodes mounted and projecting into said housing andimmersed in the representative sample passing through said housing, saidsample stream being started upon starting of said electric motor drivingsaid pump and stopped upon shutdown of said motor, a circuit from saidregulator when energized passing a current through said electrodes andthe solution therebetween, an amplifier for said current, a relayactuated by current above a predetermined value from said amplifier, andmeans controlled by said relay and actuated by current from said powertap to feed a concentrated detergent to said washing solution tomaintain detergency of said solution substantially constant.

18. A regulator for restoring at intervals the hydroxyl ion or thehydrogen ion concentration level of a solution maintained at 'a giventemperature, whenever a small reduction in the conductivity of saidsolution occurs, comprising a feeder arranged, when energized, to add tosaid solution a concentrated component thereof, electronic switchingmeans, means responsive to small changes in the specific conductance ofsaid solution, above a predetermined value, arranged to activate saidswitching means and energize and render operative said feeding meanswhen said conductivity falls to a predetermined level above saidpredetermined value and to deenergize and render said feeding meansinoperative when said conductivity rises above said predetermined level,whereby the conductivity of the solution is maintained substantiallyconstant, and an incremental means energized by said switching means andarranged in said electronic switching means to successively incrementthe amount of said concentrated component of the solution by thatpredetermined value that will substantially compensate for extraneousadditions, occurring through use, of useless conductive material to thesolution and thus maintain the ionic concentration level of requireduseful material substantially constant.

ALBERT WOODALL SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,078,645 Swingle Apr. 27, 19372,203,251 Bonner June 4, 1940 2,243,436 Mumford May 27, 1941 2,263,847Holven Nov. 25, 1941 2,299,529 Crampton Oct. 20, 1942 2,377,363 NobleJune 5, 1945 2,490,634 Keene Dec. 6, 1949

